Plastic pipes, and particularly pipes made of one of the various fluoropolymers, have achieved substantial importance because of their ability to carry highly active chemicals such as acids and bases, and particularly extremely active acids such as hydrofluoric acid, without deteriorating the pipe or allowing leakage. Better than using mechanical joints, fluoropolymer pipes may be butt welded as described in U.S. Pat. No. 4,929,293. Pipes may be welded in a shop, or may be welded in the field during installation.
Because of the uses of such plastic pipes, it is extremely important that the joints be sound and leak-proof. Previously, there has not been adequate apparatus or methods for testing the integrity of such weld joints in plastic pipes.
The joints of metal pipes, and particularly high pressure pipelines, have been subject to testing. The U.S. Pat. No. 2,817,230 to McCully shows a device for testing a weld joint in a metal pipe construction line. This cumbersome device requires that a long rubber boot be wrapped around the pipe so that the ends of the boot overlap, and then a pair of semicircular housings are clamped by bolts over the boot and onto the pipe so that high pressure gas may be applied under the boot and against the pipe weld. If the boot and the weld hold the air pressure, it is known that the weld is acceptable. The U.S. Pat. No. 4,099,405 to Hauk shows another form of device for testing a mechanical joint in a pipe.
U.S. Pat. No. 4,513,605 discloses a complicated method and device for testing welds of thermoplastic parts.
Other less pertinent joint testing devices are disclosed in U.S. Pat. Nos. 3,358,497; 4,194,389; 4,727,749; 4,860,796; and 4,879,896.